Cosmetic make-up compositions intended to apply coatings and/or colors to the skin generally fall into one of the categories: A - Dry powders in loose, cake, or compact form, B - Anhydrous fatty systems (oils and waxes) in solid, paste and liquid forms, and C - Emulsions of the oil-in-water (O/W) type in cream and lotion forms. The compositions in categories A and B do not provide moisture to the skin at all. While compositions in category C are intended to apply moisture to the skin, there is considerable loss of moisture due to evaporation during application and feathering of the composition, or within a short period after application due to the moisture being in the outer phase of the emulsion.
This shortcoming of the O/W type emulsion should in theory be overcome by switching to a water-in-oil (W/O) type emulsion, but surprisingly cosmetic preparations involving W/O emulsions have found little success in the marketplace. This appears to be due to the difficulty in preparing stable W/O emulsions which are cosmetically acceptable (i.e. not waxy, tacky, heavy, draggy) and which will carry sufficient water to have the desired skin moisturizing effect.
A search of the patent art has revealed many patents relating to water-in-oil emulsions generally, but relatively few which have any pertinence with respect to the present invention. There are, however, three prior patents which should be briefly considered at this time.
U.S. Pat. No. 3,594,409 is of interest in disclosing cosmetic W/O emulsions which may contain as much as about 66% water, but this patent is really related to, and all claims are directed to, a special type of emulsifying agent which may be referred to as magnesium salts of succinic esters of polyoxyalkylene fatty alcohols, and which are quite unrelated to the emulsifying agents of the present invention.
U.S. Pat. No. 3,102,128 teaches an ointment base indicated to be capable of forming water-in-oil emulsions by addition of up to three times by weight of water, although no specific examples of such emulsions are provided. The patent is directed to a special type emulsifier referred to as mixed esters of a pentaerythrite di-fatty acid and a citric acid di-fatty alcohol ester in a 1:1 molar ratio; and this special type of emulsifier is quite unrelated to the emulsifying agents of the present invention.
U.S. Pat. No. 3,536,816 disclosed preparation of W/O emulsions employing as emulsifier a partial ester of the monoglyceride of oleic acid but does not indicate that stable emulsions can be prepared containing more than about 43% water. Thus this patent fails to provide any teaching of the high, 60 to 80%, water content of W/O emulsions which are obtained in accordance with the present invention.